Ultrasensitive michrobiochemical techniques as well as histochemical staining methods will be used to elucidate the role of proteolytic enzymes in myelin breakdown in Multiple Sclerosis and to localize such enzymes to the cells from which they originate. The progression of the lesion will be analyzed in biochemical terms and microscopically normal white matter will be studied for incipient changes and possible early alterations in astrocytes.